Williams, 16, has completed a move to join the Fulham Academy with a compensation package agreed by the two clubs.
Chairman Pete Winkelman told the club's website: "We are very disappointed that George has chosen not to take up his scholarship or the offer of a professional contract with MK Dons and has instead decided his future is best served with Fulham. Everyone at the club wishes him well in the future."

A sign of the strength of the Dons' academy is Brendan Galloway and Dele Alli being selected in the latest England U17 squad.